Spin Transfer Torque Random Access Memory (STTRAM) is a type of magnetoresistive Random Access Memory (MRAM) which is non-volatile and is typically used for memory circuits, such as, cache, memory, secondary storage, and other memory applications. STTRAM memory may often be operated at reduced power levels and may be less expensive as compared to other memory types.
One problem encountered with STTRAM memory is that write operations to the STTRAM memory may be relatively long, as compared to read operations, thereby adversely affecting performance of the STTRAM memory. One approach to reducing the write time for STTRAM memory has been to reduce the persistence of the memory, that is, the length of time that each bit cell reliably maintains its logic state.
Other techniques are directed to improving efficiency of STTRAM memory. One such technique detects when a cell is switched and terminates the write operation for that cell to reduce excess current flowing through the ferromagnetic device.
Another type of non-volatile memory is flash memory in which the bitcells comprise NAND gates. Flash memories often have two operational modes, an erase mode in which a whole subarray is erased, and a set mode in which bits may then be set as needed.